The Lippert 334647 is a direct-replacement outboard inner arm tube assembly designed for Lippert rack-and-pinion slide-out systems equipped with an 18-tooth gear. At 70 inches long and sized at 2.5" x 2.5", this is the structural inner arm that telescopes within the outboard slide-out mechanism -- a critical component for smooth, reliable room extension and retraction. Cross-references Keystone RV part number 397776.
Lippert's rack-and-pinion slide-out systems are among the most common mechanisms found in towable RVs, including fifth wheels and travel trailers built by Keystone, Forest River, Coachmen, and others. The outboard inner arm tube is the inner telescoping member that rides inside the outer arm housing and transfers drive force from the gear mechanism to push or pull the slide room.
Over time, these tubes can develop bends, cracks, or wear at the gear interface -- particularly on heavily used slides or units that have been operated on uneven ground. Replacing the inner arm tube restores proper slide travel and eliminates binding, grinding, or incomplete extension.
2.5" x 2.5" square tube profile matches original Lippert outboard arm geometry for drop-in fitment.
Machined to interface correctly with the 18-tooth drive gear used in this Lippert slide-out series.
Full 70" arm length supports the slide travel range for rooms requiring longer outboard arm assemblies.
Matches Keystone RV part number 397776, simplifying sourcing for Keystone brand owner repairs.
Lippert rack-and-pinion slide systems use a pair of arm assemblies -- inboard and outboard -- to support and drive each slide room. The outboard inner arm tube is the inner telescoping member of the outboard assembly. It contains the rack teeth that engage the drive gear, and it rides within the outer arm tube as the room moves in or out.
When the motor drives the gear, the rack on the inner arm translates rotational motion into linear movement, extending or retracting the room. A damaged or bent inner arm tube will cause uneven room travel, gear skipping, or a room that won't fully extend or retract.
This assembly fits Lippert outboard slide-out arm mechanisms specifying a 2.5" x 2.5" inner tube and an 18-tooth drive gear. It is commonly found on:
Replacing an inner arm tube requires the slide room to be supported independently while the arm assembly is disassembled. This is a structural repair -- improper installation can result in a room that will not travel safely. The following notes apply: